The present invention relates to an apparatus for evaluating measuring values, and more particularly, to an apparatus for evaluating measuring values from moving laminar materials under test.
For the quality control and the on-line process control of laminar materials under test as for instance paper, plastic foils, webs of fabric or sheets of metal, certain characteristics of such materials under test are sensed, whereas it is known to explore the material under test with a traversing measuring device. For the exploration of paper webs, e.g., the material under test can be irradiated with infra-red (IR) radiation of different wave lengths, and by means of evaluating the :reflected or transmitted radiation intensities and by an accompanying computation the desired measured values can be evaluated. The different IR rays of different wave lengths may be produced from a single radiation source by a filter wheel and may be sensed by a detector. However, the rays of such a source could also be separated into different channels by a chopper device and a beam splitter and a filter element, and could be applied to different detectors. Examples of this can be taken from U.S. Pat. Nos. 4,300,049 and 3,405,268.
With a measuring device traversing the material under test and with the material under test being moved, a problem exists that the rays of different wavelength impinge on the material under test on different spots, such that system errors produced thereby do not allow an optimum control of the process. With respect to a high speed evaluation of the measuring data for a quick control of the quality features of the material under test, the traversing velocity of the measuring platform can be increased which results in an increase distance between the different measuring points of the sensors, and therefore results in a greater measuring error.
Thus, there is a need to provide a device for evaluating measuring values in which the measuring values can be acquired from the same measuring spot of the material under test.